Automotive vehicles incorporate a variety of restraint systems to provide for the safety of vehicle occupants. For example, it is known in the vehicle art to provide various types of seat belts or restraint systems for restraining an occupant in his or her seat and providing controlled deceleration of portions of the body to limit the forces applied to the occupant's body during rapid deceleration of a vehicle from a cause such as a collision. Various types of seat belts and restraint systems have been used in automobiles, trucks, and other vehicles and are commonly known today.
Known seat belt systems typically used in commercially available production vehicles are three-point restraint systems with a lap belt and a shoulder belt extending over one shoulder of the occupant and connecting with the lap belt. The lap belts are anchored at one end, to the seat or to the vehicle body at a point adjacent the seat. The shoulder belts are connected at one end to the vehicle or to the seat and at the other end to the lap belt or lap belt buckle mechanism.
A challenge faced by designers of known seat belt systems is to provide a load limiter. Limiting the load on the seat occupant may be a desirable approach to reducing injury. To this end systems for limiting the load on the upper portion of the shoulder belt and thus on the upper portion of the vehicle occupant's chest are known and are incorporated into a seat belt retractor or in the structure to which the seat belt retractor is mounted. According to known approaches, the shoulder belt load limiter-fitted retractor is typically mounted above and behind the occupant's shoulder. Such systems have demonstrated a reduction of load on the upper portion of the wearer's chest in an impact event.
However, during an impact event such known systems are not particularly effective at limiting the load on the lower portion of the seat belt, or, more importantly, to the lower portion of the seated occupants chest, where, in general, the lower portion of the shoulder belt meets the latch plate and, either in addition or in the alternative, the lap belt. This is because during the impact event the friction between the shoulder belt and the upper torso greatly reduces the effect of load-limiting on the lower torso. It may be too that lower chest shoulder belt forces actually contribute to chest deflection.
An alternative to the known arrangement is to make the lap belt anchor or lap belt buckle attachment itself load-limiting. While tending to reduce the lower torso-applied loads, this arrangement may also allow more pelvis excursion which would tend to raise the loads applied to the lower torso.
As in so many areas of vehicle technology there is always room for improvement related to the use and operation of vehicle seat belt systems.